Distillation can be used for the recovery of bituminous substances and oil from bituminous or oil containing mineral matter which, to the extent that the hydrocarbons can be driven from the mineral matter, can be referred to as "devolatilizable material."
Such materials include oil shale, oil sand, coal, diatomaceous earth or mixtures of these with other mineral substances and, more generally, to solid mineral matter containing volatile hydrocarbons.
The term "dry distillation" or terms of similar significance can be used to describe a process in which the mineral matter to be subjected to the dry distillation is brought into direct contact with a solid heat carrier so that a solid-solid heat transfer is effected with the bituminous or hydrocarbon components being volatilized from the devolatilizable mineral matter.
Known processes for the dry distillation treatment of such mineral substances and which contact these mineral substances with a hot fine-grain heat-transfer medium, are described in German Pat. Nos. 1,809,874 and 1,909,263, in German patent document (open app1ication) DE-OS No. 29 27 065 and in U.S. Pat. Nos. 3,655,518, 3,703,442 and 4,318,798.
The efficiency and economy of these processes can be increased by preheating the devolatilizable mineral matter by waste heat.
U.S. Pat. No. 3,265,608 describes the dry distillation of oil shale in which the devolatilizable mineral matter is mixed with the heated granular material from another source, i.e. a different material, to vaporize the oil. The heating of the granular material is effected by combustion of a fuel, and from the combustion process an exhaust gas arises which is utilized to preheat the oil shale in a riser, i.e. in an upright duct through which the oil shale is passed.
Notwithstanding the progress represented by the aforementioned patents and publications in the dry distillation of bituminous and oil-containing mineral matter, the economies of the processes leave much to be desired and afford considerable room for improvement with the aim of ensuring that the processes will be economical.